Lund University Students 3D Print Mobile Concrete Furniture and Public Art

This project began through a conversation with Helsingborg Hem, the Helsingborg city department responsible for providing housing to its citizens, who were interested in working with Lund University on developing a demo 3D printer machine to print houses. However, as with many projects undertaken without a budget, the Additive Manufacturing research team at Lund University had access to a spare ABB robot arm, so they decided to start with a smaller scale proof-of-concept system that was capable of printing street furniture, or public artworks. The idea was for a 3D printer that could be quickly wheeled into position, locked down, print a concrete bench, for example, and then be moved to the next spot to print the next object.

A brief was given to two Masters students, Borja Serra and Lars Henrik Anell, to transform the ABB IRB140 robot into a mobile 3D printer capable of printing street furniture, or public art works, in concrete. They divided up the work into two sub-projects, with Borja taking care of the 3D printer frame design, and the software and programming of the robot, and Henrik taking care of the design and construction of the concrete print-head. Here is some of what they came up with:

3D Printer Frame:
The frame for the 3D printer was built out of standard aluminium extrusion, and includes a removable bottom front linkage to make the frame completely rigid during transport, but allows extra reach to the robot when it is removed.

CAD model of the robot in its frame

Software:
The software developed for the 3D printer processes the design to printed and translates it into the robot language. It tells the robot what to do in order to create what has been designed. It first uses MATLAB to slice up the CAD design, from an STL file, as a normal 3D printer would, but then translates that into RAPID code, as is required to control the ABB IRB 140 robot. It also uses another algorithm to keep a continuous flow of concrete during the print. This is important to guarantee a good quality print and get good mechanical properties for the concrete.

Screenshot of the control printer control software

ABB IRB 140 Robot Arm

Print-head:
The design for the print-head was based on one of Prof. Olaf Diegel's earlier design of a desktop 3D printer head capable of extruding polymer in granule form (rather than the conventional filament form). One of the requirements for the project, as it was done on a low budget, was to keep everything as low cost as possible, so Henrik chose to use a 100mm hole boring auger as the mechanism to deliver the concrete to the print nozzle.

The proof-of-concept printer successfully printed the objects shown below. Future work includes improving the concrete feeding system, adding paddles to smooth the objects being printed, maybe replace the robot arm wiht a gantry type system to allow bigger prints, etc. This is an on-going project, so stay tuned to see what the next students come up with.

And the assembled printer with a pipe feeding concrete to the print-head:

And here's a video video clip, taken by Borja and Henrik, showing the printer in action. Note that this video is from the early testing phase, before a concrete feeder system had been added, so the concrete was manually shoveled into the print-head.